OpenGL Programming Guide

Chapter 6Lighting

A Simple Example: Rendering a Lit Sphere

Select a Lighting Model

As you might expect, the glLightModel*() command describes the parameters of a lighting model. In Example 6-1 , the only element of the lighting model that's defined explicitly is the global ambient light. The lighting model also defines whether the viewer of the scene should be considered to be an infinite distance away or local to the scene, and whether lighting calculations should be performed differently for the front and back surfaces of objects in the scene. Example 6-1 uses the default settings for these two aspects of the model - an infinite viewer and one-sided lighting. Using a local viewer adds significantly to the complexity of the calculations that must be performed because OpenGL must calculate the angle between the viewpoint and each object. With an infinite viewer, however, the angle is ignored, and the results are slightly less realistic. Further, since in this example, the back surface of the sphere is never seen (it's the inside of the sphere), one-sided lighting is sufficient. The section "Selecting a Lighting Model" describes the elements of an OpenGL lighting model in more detail.

OpenGL Programming Guide